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H.265 / HEVC

High Efficiency Video Coding (HEVC) is a draft video compression standard, a successor to H.264/MPEG-4 AVC (Advanced Video Coding), currently under joint development by the ISO/IEC Moving Picture Experts Group (MPEG) and ITU-T Video Coding Experts Group (VCEG). MPEG and VCEG have established a Joint Collaborative Team on Video Coding (JCT-VC) to develop the HEVC standard.

The project has tentative names H.265 and H.NGVC (Next-generation Video Coding).

HEVC aims to substantially improve coding efficiency compared to AVC High Profile, i.e. reduce bitrate requirements by half with comparable image quality, probably at the expense of increased computational complexity. Depending on the application requirements, HEVC should be able to trade off computational complexity, compression rate, robustness to errors and processing delay time.

The preliminary requirements for NGVC were bit rate reduction of 50% at the same subjective image quality comparing to H.264/MPEG-4 AVC High profile, with computational complexity ranging from 1/2 to 3 times that of the High profile. NGVC would be able to provide 25% bit rate reduction along with 50% reduction in complexity at the same perceived video quality as the High profile, or to provide greater bit rate reduction with somewhat higher complexity.

HEVC is targeted at next-generation HDTV displays and content capture systems which feature progressive scanned frame rates and display resolutions from QVGA (320x240) up to 1080p and Ultra HDTV (7680x4320), as well as improved picture quality in terms of noise level, color gamut and dynamic range.

The HEVC draft design includes various coding tools, such as:

  • Tree-structured prediction and residual difference block segmentation
  • Extended prediction block sizes (up to 64x64)
  • Large transform block sizes (up to 32x32)
  • Tile and slice picture segmentations for loss resilience and parallelism
  • Wavefront processing structure for decoder parallelism
  • Non-square transform block sizes
  • Integer inverse transforms
  • Mode-dependent sine/cosine transform type switching
  • Adaptive motion vector predictor selection
  • Temporal motion vector prediction
  • Multi-frame motion compensation prediction
  • High-accuracy motion compensation interpolation (8 taps)
  • Internal bit depth increase (IBDI)
  • Directional intra prediction
  • De-blocking filter
  • Adaptive loop filter (ALF)
  • Sample adaptive offset (SAO)
  • Entropy coding using one of two selectable types:
    • Context-adaptive binary arithmetic coding (CABAC)
    • Context-adaptive variable-length coding (CAVLC)